Nonaqueous coating materials based on fluorine-containing polymers are well established for a large number of very different end-use applications.
Thus, for example, EP-B-856 020 describes nonaqueous clearcoat materials based on fluorine-containing polyacrylate binders and on polyisocyanate group-containing crosslinking agents, these coating materials being curable to oil-, soiling-, and water-repellent coatings and being useful for the coating of vehicles, such as subway cars, trains, buses, and the like, industrial systems, such as tanks, buildings, and other edifices, for example. The clearcoat materials serve more particularly for the coating of buildings, buses, trains and other objects where graffiti is a problem, since the resultant coatings are easily cleaned and also offer high resistance toward soiling. To prepare the fluorine-containing polyacrylate binders, ethylenically unsaturated compounds are used that have fluoroalkyl groups, such as fluoroalkylethyl (meth)acrylates or 2-(N-ethylperfluorooctanesulfo-amido)ethyl methacrylate, for example. These fluorine-containing monomers, though, have to be added on their own and separately from the remaining monomers, and this makes the binders decidedly costly and inconvenient to prepare.
Moreover, information as to how it is possible to obtain surfaces which have a high hydrophobicity which is as long-term as possible and which at the same time have a very high mechanical and photochemical stability, such surfaces being required, for example, for the coating of rotor blades for wind energy systems, is no more present in that specification than is information as to how to ensure extremely rapid assembly strength and good repair adhesion. Nor is there any information as to how these qualities can be achieved in as simple and inexpensive a way as possible.
Furthermore, EP-B-856 022 discloses similar coating materials which as well as fluorine-containing polyacrylate binders comprise polyisocyanate crosslinkers in which 0.1 to 33 mol % of the isocyanate groups have been reacted with perfluoroalcohols. In the preparation—described therein—of the fluorinated polyisocyanates, high fractions of difluorinated and trifluorinated polyisocyanates are expected as well as monofluorinated polyisocyanates, and the di- and trifluorinated polyisocyanates may migrate to the film surface and hence adversely affect the overall visual appearance, the hardness, the chemicals resistance, and other mechano-technological properties of the resultant coating.
Fluorine-containing clearcoat materials are also described in WO05/030892, the binders in these clearcoat materials being fluorine-containing polyacrylates which also contain organosilane monomers in copolymerized form. The fluorine-containing polyacrylates are obtained in turn by copolymerization of ethylenically unsaturated compounds having fluoroalkyl groups, such as fluoroalkylethyl (meth)acrylates or 2-(N-ethylperfluorooctanesulfoamido)alkyl (meth)-acrylate, for example.
WO05/030891 discloses fluorinated clearcoat materials having improved clearcoat/clearcoat adhesion, these materials comprising not only a fluorinated silane polymer based on copolymerized ethylenically unsaturated compounds having fluoroalkyl groups, such as fluoroalkylethyl (meth)acrylates or 2-(N-ethylperfluorooctanesulfoamido)alkyl (meth)acrylates, for example, but also a fluorinated polyurethane resin for promoting adhesion. This resin is obtainable by reacting a polyisocyanate with a perfluorinated monoalcohol and with an oligomeric and/or polymeric polyether polyol, such as ethoxylated/propoxylated glycol, and does not contain any remaining free isocyanate groups.
WO05/080465 describes abrasion-resistant and alkali-resistant coatings that are easy to clean and are obtained using coating materials which in addition to a curable binder system and inorganic particles comprise at least one fluorine-containing oligomer or polymer having at least one functional group which is reactive with a functional group of the binder system. The fluorine-containing polymer or oligomer used comprises, for example, fluorinated polyethers, fluorinated epoxides, fluorinated polyurethanes, and fluorine-containing polymers, the fluorine-containing polymers being prepared using commercial fluoromonomers, such as tetrafluoroethylene, vinylidene fluoride, and the like.
WO07/115752 describes two-component aqueous hybrid reactive-resin systems based on polyurethane, with an epoxide/amine curing mechanism, which are used in the construction and industrial sectors for the production of easy-to-clean coatings which feature high mechanical robustness. These coating materials may optionally comprise amino- and/or hydroxy- and/or mercapto-functional, fluorine-modified macromonomers or telechelics.
Furthermore, WO05/007762 describes aqueous, optionally fluorinated polyurethane hybrid dispersions with covalently bonded fluorinated side chains, which can be introduced via the polyurethane basis and/or via radically polymerizable, fluorine-containing monomers. Using these polyurethane hybrid dispersions it is possible, by virtue of the high crosslinking density in conjunction with high hardness, to produce soiling-repellent coatings having good mechanical properties and good solvent resistance and chemicals resistance, these coatings being suitable for a very large number of different end uses.
WO08/040428 as well discloses fluorine-modified polyurethane coatings especially in the construction and industrial sectors for the permanent oil-, water- and soiling-repellent coating of mineral and non-mineral substrates.
Moreover, EP-A-2 085 442 discloses aqueous coating materials which are based on fluorosilane components and are used for the permanent oil-repellent and water-repellent surface treatment of mineral and non-mineral substrates for a variety of end-use applications.
EP-B-587 667 discloses coating material compositions based on fluorine-containing inorganic polycondensates, and used for coating glass, ceramic, metal, plastics, and paper, more particularly for coating exterior and interior mirrors and also windshields of motor vehicles.
EP-A-1 844 863 describes, likewise, coating materials for producing strongly liquid-repellent coatings, in other words coatings which develop a very large contact angle of 120° to 180° with a reference liquid, such as water more particularly. This is done using coating materials which comprise a polymer and a ceramic material or nanoparticles, and which, accordingly, lead to coatings having a textured surface. Details on the more precise composition of the polymers, however, are absent.
For surface coatings, experiments with comb polymers having fluorinated side chains have already been conducted. In this respect it is known that critical factors in achieving a low surface energy and hence good soiling repellency and water repellency properties include very long fluorinated chains and very short spacers to the main chain, in the form of hydrocarbon groups. Longer spacers, in contrast, lead to much poorer results (“Fluorinated comblike homopolymers: The effect of spacer lengths on surface properties”, Saïdi, Salima; Guittard, Frédéric; Guimon, Claude; Géribaldi, Serge; Journal of Polymer Science Part A: Polymer Chemistry, Vol. 43, issue 17, pp. 3737-3747).
Disclosed, furthermore, by Journal of Donghua University (Natural Science), Vol. 35, No. 5, October 2009, pages 547-553 is the production of a fluorinated polyacrylate emulsion by copolymerization of the reaction product of perfluorooctanol, isophorone diisocyanate, and hydroxyethyl acrylate with hydroxyethyl acrylate and octadecyl acrylate, and also the use of the resulting fluorinated polyacrylate emulsion for the coating of cotton fibers.
Chinese laid-open specification CN101020731 A, moreover, describes the preparation of fluorinated acrylate copolymers by reaction of a hydroxyl group-containing acrylate copolymer with the isocyanate group-containing equimolar reaction product of a diisocyanate with a perfluoroalkyl alcohol. These solvent-based fluorinated acrylate copolymers are used to impart water and oil repellency to leather, textile products, and the like.
There are also a multiplicity of other specifications disclosing hydrophobic coating materials for the purpose of producing water-repellent coatings. Thus, for example, EP-B-1 210 396 describes hydrophobic coating compositions for producing anti-icing coatings, said coatings being produced by chemical attachment of particles to a gel, preferably a silica-based gel, with the hydrophobicity of the surfaces being increased physically through the roughness of the surfaces.
WO96/04123 likewise describes hydrophobic coating materials for producing self-cleaning surfaces, where an artificial surface texture composed of elevations and depressions is generated, and the elevations consist of hydrophobized materials. Teflon, for example, is used for this purpose.
It is known, moreover, from WO2011/147416, for example, that the surface of wind energy systems or parts thereof, especially the rotor blades, may be provided with a strongly hydrophobic coating in order to lessen the attachment of ice, water, and soiling, since the latter may have the effect, for example, of adversely influencing the weight and aerodynamics of the rotor blades and hence reducing the efficiency of the wind energy system. Coating materials recommended include, for example, Teflon, fluoropolyurethanes, epoxy-fluorinated components, siliconized polyureas, or the like. More detailed information concerning the composition of suitable coating materials is absent from that specification as well.
It is also known from WO2011/020876, furthermore, that the surface of wind energy systems or parts thereof, especially the rotor blades, can be given a strongly hydrophobic coating based on fluorinated polyurethanes, or on polyurethanes in a blend with Teflon—again, however, more detailed information concerning the composition of suitable materials is absent from that specification.
It is known, furthermore, from EP-B-1 141 543 that the rotor blades of wind energy systems can be coated with a liquid-repellent coating material in order thus to reduce the noise emissions of wind energy systems. Examples given of suitable coating materials include not only commercial micro-silicone paints but also polyurethane paints developed for marine coating; again, however, more detailed information concerning the composition of suitable coating materials is absent from that specification.